The need to determine the location of underwater objects or objects within other surrounding media has long existed. Military and defense applications use underwater surveillance to detect enemies, torpedoes, and mines or explosives. Diving crews rely on accurate depth measurements of divers below the water surface to ensure their safety. Commercial and recreational fishermen are more generally successful if they know the depth of the fish in lakes and oceans. Biologists and other scientists track the migratory and behavior patterns of fish and other forms of aquatic life.
In World War I and World War II, sonar (originally an acronym for SOund Navigation And Ranging) technologies were developed to detect acoustic echoes from underwater objects, for example, to identify enemy submarines. Since then, a tremendous amount of research and development of sonar technologies and underwater acoustics has occurred. Today, sonar remains vital to many industries and, in fact, is taking on an ever more important role as more sophisticated warfare technologies emerge.
Sonar is a technique that uses sound propagation to navigate, communicate with or detect objects on or under the surface of the water or a surrounding medium, such as other vessels. Two types of technology share the name “sonar,” passive sonar and active sonar. Passive sonar is essentially listening for the sound made by vessels or objects, whereas, active sonar includes emitting pulses of sounds and listening for echoes. Sonar may be used as a means of acoustic location and of measurement of the echo characteristics of “targets” in the water or a surrounding medium. A target's material composition, orientation, and geometry are all factors affecting the frequency of the reflected acoustic sound. Additionally, the underwater environment consists of numerous acoustic noise sources that combine with the target's echoes, further making the unique identification of a target echo challenging. Reverberation of echoes off the floor, scattering of acoustic signals by sources other than the target, and acoustic signals generated by ships and aquatic life contaminate and inevitably degrade the signal quality of a target's echo or reflected acoustic signal. Additionally, because it depends upon properties including a target's geometry and material composition, the pulses of sounds emitted and/or reflected by the target are therefore difficult to predict.
In view of the foregoing, there is a need for improved systems and methods for identifying and locating objects within a surrounding medium.